UPTAKE OF EXOGENOUS DNA BY RAT-LIVER - EFFECT OF CATIONIC LIPIDS

We have investigated by using centrifugation methods, the uptake and t he intracellular fate of S-35 DNA by rat liver and the effect on these processes of yl)-N,N,N,-trimethylammonium-methyl-sulfate(DOTAP, Boehr inger, Mannheim, Germany), an artificial cationic lipid frequently use d in transfection experiments. Labeled DNA molecules are quickly taken up by the liver but a progressive degradation takes place with time. Subcellular distribution of the radioactivity was established after di fferential and isopycnic centrifugation. Results indicate that S-35 DN A enters liver cells by endocytosis and reaches lysosomes. The uptake of S-35 DNA is not modified if the molecule is associated with DOTAP b ut marked differences are observed after internalization of the macrom olecule. When DOTAP is used, radioactive products remain for a long ti me in low density organelles distinct from lysosomes indicating that t he transfer of internalized DNA to these organelles is delayed by the cationic lipid. These results suggest that cationic lipids could favor transfection by preventing the delivery of DNA to lysosomes, allowing these molecules to be kept intact and available for transfer from end osomes to cytosol for a long time. (C) 1995 Academic Press, Inc.